The use of algae in fish feeds as alternatives to fishmeal · · 2012-10-03Why algae? The reader...

Fishmeal is very extensively usedin feeds for fish as well as otheranimals. A recent global surveyestimatedaquacultureconsumption

of fishmeal at 3724 thousand tonnes in2006 (Tacon and Metian 2008). Now it isbecomingincreasinglyevidentthatsuchcon-tinuedexploitationof this natural resourcewillultimatelybecomebothenvironmentallyandeconomicallyunsustainable.

Any satisfactory alternative feed ingre-dients must be able to supply compara-ble nutritional value at competitive cost.Conventional land-based crops, especiallygrains and oilseeds, have been favouredalternativesduetotheirlowcosts,andhaveproved successful for some applicationswhen they were used as substitutes fora portion of the fishmeal. But even whenthese plant-based substitutescan support goodgrowth theycancausesignificantchangesinthenutritionalqualityofthefishproduced.

Why algae?Thereadermaywonderwhy

algae, includingbothmacroalgae(‘seaweeds’)andmicroalgae(e.g.phytoplankton), and which arepopularly thought of as ‘plants’,would be good candidates toserve as alternatives to fishmealin fish feeds. One fundamentalconsideration is that algae arethe base of the aquatic foodchains that produce the foodresources that fish are adapt-ed to consume. But often it isnot appreciated that the bio-chemical diversity among differ-ent algae can be vastly greaterthan among land plants, evenwhen ‘Blue-Green Algae’ (e.g.Spirulina), more properly calledCyanobacteria, are excluded

from consideration. This reflects the veryearlyevolutionarydivergenceofdifferentalgalgroupsinthehistoryoflifeonearth.Onlyoneof the many algal groups, the Green Algae,produced a line of descent that eventuallygaverisetoallthelandplants.Thereforeitcanbedifficulttomakemeaningfulgeneralisationsabout the nutritional valueof this extremelydiversegroupoforganisms;ratheritisneces-sary to consider the particular qualities ofspecificalgae.

Protein and amino acidsFishmeal is so widely used in feeds

largely thanks to its substantial contentof high-quality proteins, containing all theessential aminoacids.Acritical shortcom-ing of the crop plant proteins commonlyusedinfishfeedsisthattheyaredeficientin certain amino acids such as lysine,

methionine, threonine, and tryptophan (Liet al.2009),whereasanalysesoftheaminoacid content of numerous algae havefound that although there is significantvariation, they generally contain all theessentialaminoacids.Forexample,surveysof 19 tropical seaweeds (Lourenço et al.2002) and 34 edible seaweed products(Dawczynski et al. 2007) found that allspeciesanalysedcontainedalltheessentialaminoacids,andthesefindingsareconsist-ent with other seaweed analyses (Roselland Srivastava 1985, Wong and Peter2000,Ortizet al.2006).

Analysesofmicroalgaehave foundsimilarhigh contents of essential amino acids, asexemplified by a comprehensive study of40 species of microalgae from seven algalclassesthatfoundthat,“Allspecieshadsimilaraminoacidcomposition,andwererichinthe

essentialaminoacids”(Brownet al.1997).

TaurineOne often-overlooked

nutrient is the non-proteinsulphonic acid taurine, whichis sometimes lumped withamino acids in discussionsof nutrition. Taurine is usu-ally an essential nutrient forcarnivorousanimals, includingsomefish,but it isnot foundin any land plants. However,although taurine has beenmuch less often investigat-ed than amino acids, it hasbeen reported in significantquantities inmacroalgaesuchas Laminaria, Undaria, andPorphyra (Dawczynski et al.2007, Murata and Nakazoe2001) as well as certainmicroalgae, for example thegreen flagellate Tetraselmis(Al-Amoudia and Flynn1989),theredunicellularalga

The use of algae in fish feeds as alternatives to fishmeal

by Eric C. Henry PhD, Research Scientist, Reed Mariculture Inc., USA

table 1: nutritional profiles of rotifers enriched using optimized protocols based on culture using reed Mariculture rotiGrow Plus® and enriched with n-rich® feeds

n-rich® feed type High Pro® Pl Plus® Ultra Pl®

applications

Moderate PUFa;

overnight gut-load

maintenance

overnight or 2-6 hr

enrichment

extreme DHa 2 hr enrichment

Composition of Biomass

lipid (Dry wt. % of Biomass) 35% 44% 66%

DHa (% of lipids) 37% 41% 44%

ePa 5% 2% 0.5%

ara 1.0% 1.0% 1.2%

total PUFas 45% 45% 48%

Protein 38% 32% 18%

Carbohydrate 19% 15% 7%

ash 8% 9% 10%

Dry weight Biomass 9% 9% 9%

10 | InternatIOnal AquAFeed | September-October 2012

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September-October 2012 | InternatIOnal AquAFeed | 11

Porphyridium(FlynnandFlynn1992),thedino-flagellate Oxyrrhis (Flynn and Fielder 1989),andthediatomNitzschia(Jacksonet al.1992).

PigmentsA few algae are used as sources of pig-

mentsinfishfeeds.Haematococcusisusedtoproduceastaxanthin,which isresponsibleforthepinkcolourofthefleshofsalmon.Spirulinaisusedasasourceofothercarotenoidsthatfishessuchasornamentalkoicanconvert toastaxanthin and other brightly coloured pig-ments. Dunaliella produces large amounts ofbeta-carotene.

LipidsIn addition to its high content of high-

quality protein, fishmeal provides lipids richin ‘PUFAs’, or polyunsaturated omega-3 andomega-6 fatty acids. These are the ‘fish oil’lipidsthathavebecomehighlyprizedfortheircontributiontogoodcardiovascularhealth inhumans.But it isnotalwaysappreciatedthatalgaeatthebaseoftheaquaticfoodchaininfactoriginatethese‘fishoil’ fattyacids.Thesedesirable algal fatty acids are passed up thefoodchaintofish,andtheyareindeedessen-tialnutrientsformanyfish.

Algae have been recognised as anobvious alternative source of these ‘fishoil’ fatty acids for use in fish feeds (Milleret al. 2008), especially eicosapentaenoic

acid (EPA), docosahexaenoic acid (DHA),and arachidonic acid (ARA). There is asubstantial literature devoted to analysisof the PUFA content of microalgae, par-ticularlythoseusedinaquaculture,becausethey have long been recognised as thebest source of these essential nutrients

for production of zooplankton necessaryforthefirstfeedingoflarvalfish,aswellasfilter-feedingshellfish.

Many shellfish producers are awarethe sterolprofileof feed lipids isofcriti-cal importance, but much less attentionhas been paid to the importance of the

Macroalgae (seaweeds) of many kinds can form extensive stands with high biomass density

10 | InternatIOnal AquAFeed | September-October 2012 September-October 2012 | InternatIOnal AquAFeed | 11

FEATURE

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sterol profile of fish feeds. Aside fromalterations in thenormal sterolprofileofthe fish, thepossibleendocrineeffectsofplant phytosterols in fish feeds (e.g. soyphytohormones) have yet to be thor-oughlyinvestigated(PickovaandMørkøre2007).

Use of algae in aquacultureMany different algae already play a vital

role in aquaculture. It is widely known thatthe addition of microalgae to larval fish

culture tanks confers a number of benefits,suchaspreventingbumpingagainstthewallsofthetanks(BattagleneandCobcroft2007),enhancing predation on zooplankton (Rochaet al.2008),enhancingthenutritionalvalueofzooplankton (Van Der Meeren et al. 2007),aswellas improving larvaldigestive(Cahuet al.1998)andimmune(Spolaoreaet al.2006)functions.

Furthermore, it has also been shownthat larvae of some fishes benefit greatlyby direct ingestion of microalgae (Reitanet al. 1997). One study has even shownthatthat livezooplanktoncouldbeelimi-natedfromthelarvaldietofRedDrumifmicroalgaewere fed alongwith a formu-lated microparticulate diet (Lazo et al.).

It is not surprising that the biochemicalcompositions of certain marine micro-algae are well-matched to the nutritionalrequirements some marine fish. Larvalfeedsareprobablydeservingof themostattentionineffortstodiscoverhowalgaecan best be used in fish feeds, becausemicroalgae are a natural component ofthe diet of many larval fish, either con-sumed directly or acquired from the gutcontents of prey species such as rotifersandcopepods.Existingprotocolsthatuse

microalgae to improve the PUFA profileof live prey (Table 1) demonstrate howeffectively an algal feed can enhance thenutritionalvalueoftheselivefeeds.

Use of algae in formulated fish feeds

Variousspeciesofmacroalgaeandmicro-algae have been incorporated into fish feedformulations to assess their nutritional value,andmanyhavebeenshowntobebeneficial:ChlorellaorScenedesmus fedtoTilapia(Tartielet al. 2008);Chlorella fed to Korean rockfish(Baiet al. 2001);Undaria orAscophyllum fedtoSeaBream(Yoneet al.1986);Ascophyllum,Porphyra,Spirulina,orUlva fed toSeaBream(Mustafa and Nakagawa 1995); Gracilaria or

Ulva fed to European Sea Bass (Valenteet al. 2006); Ulva fed to Striped Mullet(Wassefet al. 2001);Ulva orPterocladia fed to Gilthead Sea Bream (Wassef et al.2005);Porphyra,oraNannochloropsis-IsochrysiscombinationfedtoAtlanticCod(Walkeret al.2009,2010).Unfortunately,it has rarely been possible to determinethe particular nutritional factors respon-sible for these beneficial effects, eitherbecausenoattemptwasmadetodoso,orpoordesignofthestudy.

Forexample,inoneofthefewstudiesthathasfocusedontheeffectsofsubsti-tutingalgalproteinforglutenprotein,thecontrol and all the test diets containedcaseinplusaddedmethionineand lysine,no analysis of the algal protein wasprovided,andthealgalprotein(abiofuelprocess by-product) contained very highlevels of aluminium and iron (Husseinet al. 2012). More and better-designedstudiesarenecessarybeforewewillhave

agoodunderstandingofhowalgaecanbestbeusedinfishfeeds.

Choosing the right algaeOften the algae chosen for fish feeding

studies appear tohavebeen selected largelyfor convenience, because they are low-costand commercially available. For example,microalgae such as Spirulina, Chlorella andDunaliella canbeproducedbylow-costopen-pond technologies and are marketed as drypowders, and their nutritional profiles are

well-documented.Macroalgaesuchasthe‘kelps’ Laminaria, Undaria, and Durvillea,and the brown rockweed Ascophyllum,occur in dense stands that can be har-vestedeconomically,andtheyhavealonghistoryofuseassourcesofiodine,assoilamendments,andanimalfeedadditivestosupplytraceelements.

In recent years there has been greatinterest in the potential of algae as abiofuel feedstock, and it has often beenproposedthattheproteinportionremain-ingafterlipidextractionmightbeauseful

input foranimal feeds(e.g.Chenet al.2010).However,thealgaechosenforbiofuelproduc-tionmaynotbeoptimalforuseasafeedinput,andtheeconomicpressureforthelowest-costmethods of fuel production is likely to resultin protein residues with contamination thatmakesthemunfitforuseasfeed(e.g.Husseinet al.2012).

Bycontrast,thehigh-valuemicroalgaethatareusedinshellfishandfinfishhatcheriesaregenerallyproduced in closed culture systems to excludecontaminating organisms, and they cannot bedriedbeforeusewithoutadverselyaffectingtheirnutritionalandphysicalproperties,greatlyreduc-ingtheirvalueasfeeds.Inevitablytheirproductioncostsarehigher,buttheirexceptionalnutritionalvaluejustifiestheextraexpense.Table2presents

table 2: Because these algae are produced using continuous-harvest technology that maintains exponential growth, their protein and lipid contents are comparable to those provided by fish feeds.

(Dry Weight)nannochloropsis

oculatatetraselmis sp. Pavlova sp. Isochrysis

(t-Iso)thalassiosira weissflogii

Protein 52% 55% 52% 47% 52%

Carbohydrate 16% 18% 23% 24% 23%

lipid 17% 14% 20% 17% 14%

Various species of microalgae are used as aquaculture feeds, depending on the cell size and nutritional profile needed for particular applications


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typical nutritional profiles of algae produced byReedMaricultureInc.

Justas itwouldbesenseless toarbitrarilysubstitute one conventional crop plant foranother (e.g. potatoes for soybeans) whenformulating a feed, the particular attributesof each alga must be carefully considered.Inaddition to theprotein/aminoacidprofile,lipid/PUFA/sterolprofile,andpigmentcontent,thereareimportantadditionalconsiderations.

The type and quantity of extracellularpolysaccharides,whichareveryabundantincer-tainalgae,caninterferewithnutrientabsorption,orconverselybeusefulbindingagentsinformingfeed pellets. The thick cell walls of microalgaesuchasChlorellacanpreventabsorptionofthenutritional valueof the cell contents. Inhibitorycompounds such as the phenolics producedby some kelps, and brominated compoundsproduced by red algae such as Laurencia, canrenderanalgawithanexcellentnutritionalanaly-sisunsuitableforuseina feed. Depending ongrowth and process-ing conditions, algaecan contain high con-centrations of traceelements that may bedetrimental.

Fur ther carefulstudy of the prop-

er ties of numer-ous algae will benecessary in ordertooptimallyexploitthe great potentialoffered by thisdiverse group oforganisms. But it isalready apparentthat algae will playan important partin the effor t tomove the formula-tion of fish feed“down the foodchain” to a moresustainablefuture.■

Referencesavailableonrequest

More inforMation:Eric C. Henry PhD, Reed Mariculture Inc.Tel: +1 408 426 5456Fax: +1 408 377 3498Email: [email protected]: www.reedmariculture.com


FEATURE

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The annual global production offishmeal and fish oil is currentlyaround fivemilliontonnesofmealand one million tonnes of oil

(Figure1),except inyearswhen the fishingintheSouthPacificisdisruptedbythewarmwatersofanElNiňo,mostrecentlyin2010.Around 22 million tonnes of raw materialis used,ofwhich approximately 75percentcomesfromwholefishand25percentfromby-products of processing fish for humanconsumption(IFFOestimates).

The majority of the whole fish used aresmallpelagicfishsuchasanchovy,menhaden,sardinesandsandeelsforwhichtherearelim-itedmarketsfordirecthumanconsumption.Inadditiontotheestimated11.5milliontonnesof smallpelagic fishused in fishmeal there isalsoanestimatedfivemilliontonnesofotherfish, the majority from mixed tropical trawlfisheriesinEastAsia.

Going forward The prospects for increasing the produc-

tionof fishmeal and fishoil are very limited,

sincemostoftheunderlyingfisheriesarenowbeingwellmanaged, using the precautionaryprinciplewithtightlysetandmonitoredquo-tas.Alsoincreasingly,marketsarebeingfoundforatleastaproportionofthecatchestogofordirecthumanconsumption.

Inaddition there isconcern that someofthemixedtropicaltrawlfisheriesarenotbeingwellmanagedandthatcatcheswillthereforedecreaseinthecomingyearsasthesebecomeseverelydepleted.Theprospectsforincreas-ingvolumesoffisheriesby-productsdohow-ever lookbetteras fishingbecomesconcen-tratedat fewer landingsitesandaquaculturalproductionalsobecomesmoreconcentrated.Thiswillbe furtherencouragedby the risingpriceoffishmealandstricterlawsagainstthedumpingofwastematerial.Soonbalancetheproductionofbothfishmealandfishoiloverthe next few years is likely to remain aboutwhereitisorpossiblydecreaseslightly,whichwillcertainlyhappeninElNiñoyears.

The lack of growth in the production ofmarineingredientshasledsometospeculatethatthegrowthofaquaculturewouldinturnbelimitedbytheshortageofsuchkeyingredi-

ents–theso-calledfishmealtrap.Itiscertainlytrue that during the 1990s and early 2000sasaquaculturegrew, itusedmoreandmorefishmeal,mostlybytakingvolumesthatinthepasthadgoneintopigandpoultryfeeds.

However, since around2005 aquaculturerequiringfeedhascontinueditsstrongannualgrowth of around seven percent but thevolumesoffishmealusedinaquaculturehaveremainedsteadyataround3.2milliontonnesand those of fish oil have even reducedto around 600,000 tonnes. (Figure 2). Thishas led the FAO to state in their recentlyreleasedreportontheStateofFisheriesandAquaculture(FAO2012):“Althoughthedis-cussionontheavailabilityanduseofaquafeedingredients often focuses on fishmeal andfish-oil resource, considering the past trendsand current predictions, the sustainability oftheaquaculturesectorwillprobablybecloselylinkedwiththesustainedsupplyofterrestrialanimal and plant proteins, oils and carbohy-dratesforaquafeeds.”

Becoming a strategic ingredientThis growth in aquaculture production,

Fishmeal & fish oil and its role in sustainable aquaculture

by Dr Andrew Jackson, Technical Director, IFFO, UK

Figure 1. The Global Production of fishmeal and fish oil from 1964-2011 (IFFO data)

Figure 2. The global production of fed aquaculture and the use in the associated diets of fishmeal and fish oil, millions of tonnes (FAO FishStat data and IFFO data and estimates)


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whilst not increasing the total amount offishmeal used, is coming through the partialreplacementoffishmealinthedietsofalmostall species (Taconet al2011,Figure3).Thisdrive to replace fishmeal is being driven bytheriseinthepriceoffishmealandimprovingnutritional knowledge, but also by concernabout the fluctuating supply due to ElNiño,etc. Of course the price of all commodi-

ties has risen steeply inrecent years and it isimportant to comparethe price of fishmealwiththealternatives.

Themostcommonlyused alternative to fish-meal is thatofsoymeal.Figure4showsthatoverthelasttwentyyearsthepriceratiooffishmealtosoymeal has increasedsignificantly, which isindicative of the factthat fishmeal is beingreduced in less criticalareas such as growerfeeds, but remains inthe more critical andlessprice-sensitiveareasof hatchery and brood-stock feeds. Fishmeal isthereforebecomingless

of a commodity and more of a strategicingredient used in places where its uniquenutritionalpropertiescangivethebestresultsandwherepriceislesscritical.

Fish oil and its fatty acidsAshasbeenwelldocumented,duringthe

period1985-2005fishoilusagemovedfrombeing almost exclusively used to produce

hydrogenated margarines to being almostexclusivelyusedinaquaculture.Withinaqua-culturebyfarthebiggestuserwasinsalmonfeed, indeed it reached the point, in around2002, when over 60 percent of the world’sfishoilproductionwasbeingfedtosalmon.

The reason for this very high usage insalmonfeedswasthatsalmonwerefoundtoperform best on diets with in excess of 30percentfatandatthetimefishoilwasoneofthe cheapest oils on the market. In additionit also gave the finished salmon fillets a veryhighleveloflongchainOmega-3fattyacids,specificallyEPAandDHA.

During the last 10 years increasing evi-dencehasbeenpublishedontheveryimpor-tantrolethesetwofattyacidsplayinhumanhealth.EPAhasbeenshowntobecritical inthe health of the cardiovascular system andDHAintheproperfunctioningofthenervoussystem,mostnotablybrainfunction.

Thisgrowingawarenesswithinthemedicalprofession and the general public has led tomanygovernmentsproducingrecommendeddailyintakesforthesefattyacidsandcompa-nies launchinga largenumberofhealth sup-plements, including pharmaceutical products,withconcentratedEPA.

TheimportanceplacedonEPAandDHAin the human diet has had a number ofprofoundeffectsonthefishoilmarket.Firstlyoverthelasttenyearsasignificantmarkethas

Figure 3. The dietary inclusion of fishmeal (%) in aquaculture feeds over the period 1995-2010 (after Tacon et al 2011 )


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developedforthesaleofcrudefishoilforitsrefinementandinclusionintocapsulesetc.

This has grown from almost nothing, tothe point where today around 25 percentof theworld’sproductionofcrude fishoil issold to this market. This has occurred at atimewhen thedemand for salmon feedhasgonefrom1.8milliontonnestonearlythreemilliontonnes.Theothercriticalfactoristhattoobtainfishoiloftherightquality(freshness,lackofoxidationproductsand levelsofEPAand DHA) the nutraceutical market pays apremiumof25-30percentoverthatforfeedoil (current price for feed-grade fish oil isapproximately$1,800/tonne).

In order to increase the production ofsalmonfeedin-linewiththemarket(aswell

as tryingtominimiseanypriceeffect) feedproducershavebeen increasinglysubstitut-ingfishoilwithvegetableoil.Thevegetableoil of choice is rapeseed (or canola) oil,which,while not having any EPAorDHA,doesatleasthaveshort-chainomega3fattyacids and fewer omega-6 fatty acids thanmost other commonly available vegetableoils such as soya oil. The point has nowbeen reached where over 50 percent ofthe added oil in salmon diets comes from

vegetable sources and this trend seemslikelytocontinue.

As salmon are poor converters of short-chained omega-3 fatty acids to long-chainfattyacidsthefattyacidprofileofthefinishedsalmon fillet is verymucha reflectionof thefattyacidprofileinthefeed.TheresultisthattheEPAandDHAcontentoffarmedsalmonis decreasing and the omega-6 content isincreasing.

This trend seems set to continue in theyearstocome.Itseemslikelythatthesalmonmarket will differentiate into ‘high EPA andDHA’ salmon demanding a price premiumandregularsalmon,which,whilestillcontain-ingsomeEPAandDHAwillhavelevelswellbelowthatfoundinwildsalmon.

Is it sustainable?One of the most often asked questions

about fishmeal and fish oil is whether ornotthepractice issustainable.This isahugetopicfordiscussionandonethatisnoteasilycovered in the last sectionofa shortarticle.Toanswer thequestiononehas togobackandlookatthesourceoftherawmaterialandlookatthematter,fisherybyfishery.Themostwidelyacceptedmeasureof sustainability fora fishery is theMarineStewardshipCouncil’s

standard. However, whilst this has beenadopted by a growing number of fisherieswhichcanbeeco-labelledatthepointofsale,therearecurrentlynosubstantialvolumesofwhole-fish fromMSCcertified fisheriesbeingmadeavailabletofishmealplants.

Back in 2008 IFFO became aware thatthe fishmeal and fish oil industry needed anindependently set, third-party audited stand-ard, which could be used by a factory todemonstratetheresponsiblesourcingofrawmaterial and the responsible manufacture ofmarine ingredients. IFFO convened a multi-stakeholdertaskforceincludingfeedproduc-ers,fishfarmers,fishprocessors,retailersandenvironmentalNGOswhooverthenext18months complied the standard which waslaunchedlate2009.

The IFFO RS standard has been quicklyadopted by the industry and the point hasnowbeen reachedwhereoverone thirdofthe world production comes from certifiedfactories. The standard requires that anywhole fish must come from fisheries thataremanagedaccordingtotheFAOCodeofConductforResponsibleFisheries.Thestand-ardalsodemandsthatthefactorycandemon-strate good manufacturing practice includingfulltraceabilityfromintaketofinishedproduct.

Therearenowaround100certifiedfacto-riesinninedifferentcountriesproducingIFFORS fishmealand fishoil.Manyof theworld’smajor feed fisherieshavebeenapproved foruse,althoughsomehaveyettoproducesuf-ficientevidencetoconvincetheauditors.Fulldetails of certified plants and approved rawmaterialscanbefoundontheIFFOwebsite,www.iffo.net.

A continuing area of concern is Asiawhere,asdiscussedearlier,thereareconsid-erable volumes of fishmeal produced fromtrawledmixed species. IFFO isworkingwitha number of different organisations includ-ing the FAO and the Sustainable FisheriesPartnershiptoinvestigatehowtobringaboutfisheriesimprovementinthiscriticalarea.Asia

Figure 4. The ratio of the price of Peruvian fishmeal and Brazilian soymeal based on weekly prices for the period 1993-2012 and the calculated trend line (IFFO data)


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is the region where aquaculture is growingfastestandtheneedforresponsiblyproducedfishmealishighest.

ConclusionsFishmealandfishoilproductionisexpect-

ed to remain around current levels, but thisisunlikely to limit thegrowthofaquaculturewhichwillcontinuetohavereducinginclusionlevels of marine ingredients in the diets ofmost farmed fish. Fishmeal will increasinglybecomeastrategic ingredientusedatcritical

stages of the life-cycle when optimum per-formanceisrequired.

ThegrowingimportanceofEPAandDHAin human health will ensure that there is astrong demand for fish oil, either for directhumanconsumptionorvia farmedfish,suchassalmon.

There is a growing need for fish feedproducers and farmers to demonstrate thatall the raw materials in their feeds are beingresponsibly sourced. This is best achieved byusing an internationally recognised certificationstandard.Increasingvolumesofcertifiedmarineingredients are now coming onto the marketwhich will allow fish farmers to demonstratetheircommitmenttoresponsibleaquaculture.

References

FAO(2012).Thestateoftheworldfisheriesandaquaculture2012.Rome:FAO.

Tacon,A.G.J.,Hasan,M.R.,andMetian,M.(2011).Demandandsupplyoffeedingredientsforfarmedfishandcrustaceans-Trendsandprospects.In:FAOfisheriestechnicalpaper,Vol.564.Rome:FAO.

More inforMation:Website: www.iffo.net

"Fishmeal and fish oil

production is expected to

remain around current levels,

but this is unlikely to limit

the growth of aquaculture

which will continue to have

reducing inclusion levels of

marine ingredients in the

diets of most farmed fish"


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Feed for fish and shrimp raised inaquaculture needs high levels ofprotein and energy. Traditionallyfeed for carnivorous or omnivo-

rous fish and for shrimp provides thesemainly as fishmeal and fish oil, whichalso contributes to the health promotingaspects of fish and shrimp in the humandiet.

Aquaculture of fed species today takes60–80percentof the fishmealand80per-cent of the fish oil produced, mainly fromtheindustrialpelagicfisheriesor,inagrow-ing trend, from the trimmings producedduring processing for human consumption.Trimmingsaredefinedasby-productswhenfish are processed for human consump-tion or if whole fish is rejected becausethequalityat the timeof landingdoesnotmeet requirements for human consump-tion. The International Fishmeal and FishOil Organisation estimates trimmings arenowusedforaround25percentoffishmealproduction.

The industry is, therefore, heavilydependent on marine resources but pro-duction from these resources cannot beincreasedsustainably,eitherforhumancon-sumptionortheindustrialfisheries.Atbest,sustainably managed fisheries will continueto yield around the current harvest of fivemillion tonnes of fishmeal and one milliontonnesoffishoil.

FeedproducerssuchasSkrettingrequiretheir marine raw material suppliers todocumentthatthefishmealandfishoilarederivedfromresponsiblymanagedandsus-tainablefisheriesanddonotincludeendan-geredspecies.Therefore,tomeetagrowingdemand for fish, aquaculture must identifyalternativestothesemarineingredients.

Rising demandAnalyses of global demographics, widely

publicised by the Food and AgricultureOrganizationof theUnitedNations (FAO),indicateacontinuingexpansionofthepopu-lationpassingninebillionby2050.Inparallel,economicdevelopmentisprovidingagreaterproportion with an income that permitsthemtobemoreselectiveabout theirdiet.Themain trend is to switch fromvegetablestaplestoanimalandfishprotein.Athird,butlesser,factoristhegrowingawarenessof the health benefits of fish in the diet,providing long chain omega-3 polyun-saturated fatty acids (LC PUFAs) EPAand DHA, fish proteins and importantvitaminsandminerals suchas iodineandselenium.

At the same time, a growing propor-tion of the pelagic catch, which includesthe industrial fisheries, is going to themore lucrative markets of processing forhuman consumption, as processing tech-nology improves and as new consumerswith different tastes enter the market.Simultaneously, theomega-3supplementsindustry is competing for the best qual-ity fish oils and readily outbids the feedproducers.

According to the FAO report‘The State of World Fisheries andAquaculture 2012’, aquaculture is “setto remain one of the fastest grow-ing feed sectors”. Having doubled inthe past decade to almost 60 milliontonnes globally, it is expected to growby up to 50 percent in the next. Thismakesidentifyingalternative,sustainablesources of protein and energy a majorpriority. Researchers are looking foralternatives that will provide low feedconversion ratios, maintain high fish

welfare and produce fish that are goodtoeat,both intermsofeatingexperienceand nutrition. It has been amain focus atSkrettingAquacultureResearchCentreforthepast decade, for exampledeterminingthe nutritional value of more than 400raw materials. These investigations ledto AminoBalance™, where balancing ofamino acids increases the contributionsuchproteinsmaketomusclegrowth.

Options and challenges of alternative protein and energy resources for aquafeed

by Dr Alex Obach, Managing Director, Skretting Aquaculture Research Centre, Norway

Figure 1: Raw material options for fish feed (Source Skretting)

Protein raw materials Fats Starch

sources

Fish meal Fish oil Wheat

Krill meal Krill oil Barley

algal meal algal oil Sorghum

Soya products rapeseed oil tapioca

Sunflower meal Soybean oil Potato starch

rapeseed meal Sunflower oil Peas

Corn gluten Corn oil Faba beans

Wheat gluten linseed oil oats

Faba beans Palm oil

lupins Camelina oil

Pea meal Poultry fat

rice products lard

Poultry meal

Feather meal

Blood meal

Meat and Bone meal

Microbial protein

Insect meal

Worm meal

DDGS

Marineorigin

Vegetablerawmaterials

Animalby-products

Otherrawmaterials


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Recent advanceResearchprogresstodatemeansfishmeal

levels in feeds for species such as Atlanticsalmonhavebeenreduced.Untilrecently25percentappearedtobethelimitbelowwhichperformancesuffered,intermsofgrowthrateandfeedconversionratio.

In2010researchersatSkrettingARCfinal-isedanewconceptknownasMicroBalance™.MicroBalance™ technology is based on theidentificationof several essentialmicro-nutri-ents in fishmeal that were shown to be thelimiting factors, not the amount of fishmeal.Supplementing the diet with the right bal-ance of essential micro-nutrients and otherfunctional micro-ingredients helped reducefishmealcontentinfishfeed.

Applying the concept enabled Skrettingcompaniestoproducecommerciallysuccess-ful feedswithas littleas15percent fishmealwithout detracting from feed performance,fish welfare or end product quality. A keyadvantage of MicroBalance is the flexibil-ity toadapt the rawmaterial combination inresponse toprices, lessening for farmers theimpactsofpricevolatility.

Today Skretting can formulate fish feedwith levels of fishmeal as low as 5–10percent. Fishmeal canbe replaced solelybyvegetablerawmaterialsorbyacombinationofvegetablerawmaterialsandnon-ruminantprocessed animal proteins (PAPs). It shouldbenotedthatPAPsarewidelyusedincoun-triesoutside theEUandprovideextremelygood quality, safe nutrition to supplementfishmeal.

Typicalexamples includebloodmealalsoknown as haemoglobin meal, poultry meal,and feather meal. PAPs were banned fromanimal feed and fish feed in the EU follow-ing the BSE crisis in the 1990s. Recently aproposal for the reintroduction of PAPs in

fish feedwasapprovedbyaqualifiedmajor-ityofEUmember states,meaning thatnon-ruminantPAPswillbeauthorisedforfishfeedfromJune1,2013.

Trial resultsA22-monthtrialwithAtlanticsalmonin

a commercial scale farm in Norway dem-onstrated thepracticality ofMicroBalance. Itfollowedacom-plete genera-tion of salmonfrom smolt toharvest. Thetrial was jointlyorganised byMarine Harvestand Skrettingand conductedat the Centrefor AquacultureCompetence(CAC) inNorway fromMay 2009 toFebruary 2011inclusive. CACisacommercial-scale R&D farmmanaged byMarine Harvestand isequippedto measure alloperationalparameters justas precisely asin a small-scaleresearch sta-tion. A totalof 780,000

Atlanticsalmonprovidedweredividedandfedononeofthreefeeds:

Conventional grower feed (preMicroBalance): 25 percent fishmeal and 13percentfishoilwithEPA+DHAcomprisingabout10percentoftotalfattyacids.

OptiLine from Skretting Norway (usingMicroBalance): 15 percent fishmeal and 13


FEATURE

percentfishoilwithEPA+DHAcomprisingabout10percentoftotalfattyacids.

Experimental OptiLine (usingMicroBalance): 15 percent fishmeal and ninepercentfishoilwithEPA+DHAcomprisingabouteightpercentoftotalfattyacids.

The parameters monitored weregrowth, FCR, quality, health, sustainabilityand food safety. The total harvest weightwas 3,517 tonnes. After the harvest thetaste, smellandtextureof the filletsweretested by a panel of professional tasters.Theresultsshowedthatbothlowfishmealfeeds gave the same growth and FCR asthecontroldiet.Therewerenoobserveddifferences in fish health, or in thequalityparameters.

The salmon fed with the lowest propor-tionofmarineproducts(15%fishmeal,9%fishoil)onlyneeded1.07kgof fish in their feedtoproduce1kgatharvest.Calculatingproteinalone showed a positive ratio, with fish outexceedingfishin.

MicroBalance is now applied in the dietsofseveralothercommercialspecies,includingsea bass, sea bream, rainbow trout, turbotandyellowtail.

Fish oilResearch to date has enabled produc-

ers of fish feed to supplement fish oil withvegetableoilsinthedietsofcarnivorousspe-ciesbyasmuchas50percent.Lower levelshave been tested in experimental dietswithno negative effects. Much of the progressresultsfromtheEURAFOAproject.RAFOAstands for Researching Alternatives to FishOil in Aquaculture and the project focusedon four species; Atlantic salmon, rainbowtrout, sea bass and sea bream. Led by theInstitute of Aquaculture at the University ofStirling,partners includeNIFES (theNationalInstituteofNutrition andSeafoodResearch)and Skretting ARC, in Norway, the INRA(National Institute for Agronomic Research)in France and the University of Las Palmas,intheCanary Islands(Spain).Themainchal-lenge is to maintain adequate levels of EPA

andDHA,bothforthefishandforthehealthbenefitsoffishasfood.

SecondlytheEUAquaMaxproject,coordi-natedbyNIFESinNorwaywith32internationalpartnersaroundtheworldincludingSkrettingARC,addressedthisissuedirectly,developingdiets with low levels of both fishmeal andfish oil and thus reducing the fish-in fish-outratios.Thiscom-plements workatSkrettingARCto develop theLipoBalance™concept, whichallows combina-tions of oils tobepreparedthatwill provide thecorrect balanceof energy andnutrients, includingEPAandDHA,at lowestcost.

Performance ratiosFeed conversion ratios (FCRs) have

advanced significantly over the past threedecades. InAtlanticsalmon,forexample,theFCR has decreased from 1.30 in the 1980sto slightly above 1.00 today, mainly due tothedevelopmentofhigh-nutrient-densedietsand to improvements in feed management(reducing feedwaste).This representsmoreefficient useof feed rawmaterials; especiallyasfishmealandfishoilcontentswerereducedinthesameperiod(Table1).

Another contributor here is the emer-genceoffunctionaldietsthatmaintainorevenimprove performance in adverse conditionssuchashighor lowwater temperaturesandoutbreaksofdisease.Bettergrowth,reducedFCRandhigher survivalwill all contribute toimprovetheutilisationoffeedresources.

Feed Fish Dependency Ratio (FFDR) isthequantityofwildfishusedperquantityofcultured fishproduced.Thismeasurecanbeweighted for fishmeal or fish oil, whichevercomponent creates a larger burden of wildfishinfeed.InthecaseofAtlanticsalmonfor

example, following the introduction of theMicroBalanceconcept,thefishoilwillcertainlybethedeterminingfactorfortheFFDR.Thedependency on wild forage fish resourcesshould be calculated for both FM and FOusingthefollowingformulae.FFDRm=(%fishmealinfeedfromforage

fisheries)x(eFCR)/22.2FFDRo = (% fish oil in feed from forage

fisheries)x(eFCR)/5.0Where:eFCR is the Economic Feed Conversion

Ratio; the quantity of feed used to producethequantityoffishharvested.

Only fishmeal and fish oil that is deriveddirectlyfromapelagicfishery(e.g.anchoveta)istobeincludedinthecalculationofFFDR.

Theamountoffishmealinthedietiscalcu-latedbackto livefishweightbyusingayieldof22.2%.Thisisanassumedaverageyield. Iftheyield isknowntobedifferent that figureshouldbeused.

Theamountoffishoilinthedietiscalcu-latedbacktolivefishweightbyusingayieldoffivepercentThisisanassumedaverageyield.

Iftheyieldisknowntobedifferentthatfigureshouldbeused.

Using these formulae it can be seen thatthe FFDRs for Atlantic salmon, for example,were halved between 2004 and 2011. TheFFDRmwas reduced from1.24 to0.56 andthe FFDRo from 4.28 to 2.05. This doublesthequantityofsalmonproducedfromagivenquantityoffishmealandfishoil.

Health benefitsAsmentioned,maintaininghealthbenefits

isakeyobjectivewhenreducingdependencyonmarinerawmaterials.Itisbeingaddressedinseveralways.Thefirst istodeterminetheminimumlevelsofEPAandDHAthatthefishrequire.Thefeedswithhigh levelsofmarineingredients produced fish with high levels oflong chain (LC) poly-unsaturated fatty acids(PUFAs); more than needed by the fish sothataproportionwasmetabolisedforenergy.Atlowerinclusionlevelstheuseoftheselim-itednutrientscanbeoptimised,sinceahigherproportionwillberetainedinthemuscle.Atevenlowerlevels(closetonutritionalrequire-ment) the fish can maximise its capacity toelongateanddesaturate,andcouldbecomeanetproducerofLCPUFAs.

Figure 2: Supply and use of fish oil (Source IFFO and Skretting)

table 1: total production of fed species in 2000, 2005, 2010, with total feed used, total fishmeal and total fish oil (x 1,000 tonnes).

Year total production of fed species

total of feeds used

total fishmeal used

total fish oil used

1995 4,028 7,612 1,870 463

2000 7,684 14,150 2,823 608

2010 21,201 35,371 3,670 764

Source: Tacon et al. FAO Fisheries and Aquaculture Paper 564


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On average 100 g of salmon fillet hasaround16 gof fatofwhich at least four tofivepercentisomega-3EPAandDHA(DHAbeingthemain fattyacid inthephospholipidfraction).Thusa130gportionwouldprovidearound 930 mg of EPA and DHA. That isequivalent to several supplement capsules.TwoportionsaweekadequatelyprovidetherecommendeddietarylevelsofLCPUFAsandimportant vitamins and minerals in an easilyassimilatedform.

Asecondapproach istoexplorewaysofformulating feed so that the LC PUFAs areretainedinthefilletflesh.FurtherresearchatSkretting ARC into the functions of micro-ingredientsrecentlyledtoanewsalmonfeedthatsignificantlyimprovesthefeedconversionratioandfilletyield.Filletanalysisrevealedthemicro-nutrientsalsoraisedtheproportionofEPAandDHAinthemuscle.

Thethirdapproachistoidentifyalternativeresources. There are twomajor contenders:genetic modifications to crop plants andmicro-algae. Progress is being monitored byfeedproducerskeentoreducetheirdepend-ence on marine ingredients. Some plantsproducePUFAs,forexamplerape(canola)orsoya,butthecarbonchainsaretooshort.TheEPAcarbon chainhas20 carbon atoms andDHA22.Theambitionistointroducegenesto extend 18-carbon chains already present.

LimitedprogresshasbeenwithEPA.DHAisagreaterchallenge.

Somemicro-algaespeciesarenaturalsyn-thesisersof the longer chain fatty acids. Thechallenge here is economic; to grow themin bulk, either by sea farming or in vats onland, in sufficient volumes to make themcompetitive as a feed ingredient. There arealso reports of extracting LC PUFAs fromyeastculturesandthesewouldfacethesameeconomicchallenge.

ConclusionAqua feed producers must find alterna-

tives to themarine ingredients fishmealandfish oil while maintaining fish welfare andaquaculture performance as a highly effi-cientmeansofproducingnutritiousprotein.Eatingqualityandhealthbenefitsareequallyimportant.

However,althoughthesupplyofmarineingredients from the wild catch is limited,withappropriatecontrolstheywillcontinuetobeavailable.Akey task for the industryistoensuretheyareusedinamannerthatspreadsthebenefitsthroughacombinationof supplementation, feed formulation andfeed management on farm. This way thegrowingdemandforfishcanbemetandthebenefits shared sustainably for generationstocome.

About the authorAlex Obach has held the positionof Managing Director at SkrettingAquaculture Research Centre sinceMay1,2007.OriginallyfromBarcelona,Spain,heisaveterinarianwithaMasterin Aquaculture from the Universityof Girona (Spain) and a PhD in fishpathology and immunology from theUniversityofWestBrittany(France).HestartedworkingatSkrettingAquacultureResearchCentrein1993asaresearch-er, initially within fish health then asa nutritionist. He He previously wasManager of ARC’s Fish Health depart-ment.Between1993-1995,hewasalsoengagedaslecturerattheUniversityofBarcelona, and worked for two yearsas Manager of the Marine HarvestTechnicalCentre.


FEATURE

The world demand for seafood isincreasing dramatically year by year,although an annual upper limit of100million tons is set soasnot to

exhaustreserves.Itisforthisreasonthatthereis a considerable move towards modernisingandintensifyingfishfarming.Tobeeconomicallyviable,fishfarmingmustbecompetitive,whichmeans that feed costs amongst others mustbecarefullymonitoredastheoperationalcostgoes 60 percent for feed alone. Thereforeselection of cheaper and quality ingredientsis of paramount importance for sustainableand economical aquaculture. Identification ofsuitablealternateproteinsourcesforinclusionin fish feeds becomes imperative to counterthescarcityoffishmeal.

In addition to its scarcity and high cost, often fishmeal is adulterated with sand, salt and other undesirable materials. All these factors have forced fish feed manufactures all over the world to look for alternate sources. In this context they have been left with no protein but to substitute animal protein with plant protein sources. A variety of plant protein sources including soybean meal, leaf protein concentrate and single cell protein have been tested. The tests have shown that these can be included as alternatives to fishmeal (Ogino et al, 1978, Appler and Jauncy, 1983).

Of various plant protein sources, soybean meal (SBM) is one of the most promising replacements for part or whole of fishmeal. Soybean meal is the by-product after the removal of oil from Soya beans (glycine max). At present soybean meal is the most important protein source as feed for farm animals and as partial or entire replacement of fishmeal?

The products obtained from soybeans and their processing are as follows:-

• Soybean meals, solvent extract• Soybean meal from dehulled seeds, sol-

vent extracted,• Soybean expeller• Soybean expeller from dehulled seeds• Full fat soybean meal• Full fat soybean meal from dehulled seeds

The chemical composition of soybean meal is fairly consistent (Figure 1).

The crude protein level depends on the soybean meal quality. Soybean has one of the best amino acid profiles of all vegetable oil meals. The limiting amino acids in soybean meal are methionine and cystine while arginine and phenylalanine are in good supply (New, 1987).

The fat content of the solvent extracted soy-bean meal is insignificant but soybean expeller has oil content between six and seven percent, while full fat soybean expeller has oil content between 18 to 20 percent. Soybean meal and soybean expeller are lower in macro and trace elements than fishmeal. There is no substantial difference between the indi-vidual soybean meal products. The calcium content is low and the phosphorus level is rather higher. However, the phospho-rus is bound to phytic acid and its availability for aquatic animals is, therefore, limited.

Soybean meals and expel-lers are reasonable source of B-vitamins. For most vitamins there are insignificant differences between the different products. However the full fat soy-bean meal tends to be higher in some vitamins. While the products are mainly higher in choline content, the vitamin B12 content is low and pan-tothenic acid is mainly damaged by heat treatment.

The digestible energy of soybean meal over all fish species ranges from 2572 to 3340 Kcal/kg (10.8 to 14.0 MJ/kg). The metabolisable and digestible energy of full soybean meal increases with the increase heating temperature at a given time due to the inactivation of trypsin inhibitors.

Deleterious constituents of soybean products

Trypsin inhibitors: - About six percent of the total protein of soybeans reduces activities of trypsin and chymotrysin, which are pancreatic enzymes and involved in protein digestion (Yen et al., 1977). The activity of trypsin inhibitor is not fully understood, but is responsible for the poor performance of certain fish species (Alexis et al., 1985, Balogum and Ologhobo., 1989).

Lectins: - This type of toxic protein is chemi-cally hem agglutinin, which causes agglutination of RBC's (Liener, 1969). There are indications that lectins reduce the nutritive value of soybean meal for Salmonids but are inactivated by treat-ment of the meals (Ingh et al, 1991).

Other properties: - Soybean is unpalatable for some fishes such as Chinook salmon. While as herbivorous and omnivorous species are less choosy. The size or age of the fish may also affect the palatability of soybean meal.

Utilisation of Soybean Products in Aquaculture

Comprehensive research work has been done to evaluate soy-bean meals as a replace-ment of animal protein sources in diets for fishes but the replacement of all fishmeal by soybean meal has not been very successful perhaps due to the limiting amino

acids and insufficient heat treatment of the soy-bean meals. Smith et al (1980) claimed success in feeding rainbow trout a diet based almost entirely on raw materials of vegetable origin containing 80 percent full fat roasted soybean. In a similar report, Brandt (1979) evaluated a diet based entirely on plant ingredients (containing 50 percent heated full fat soybean + 10 percent maize gluten meal to overcome a possible defi-ciency of S-amino acids).

Reinitz et al (1978) observed that rainbow trout fry fed a diet containing 72.7 percent full fat soybean had a greater daily increase in length and weight with an improved feed conversion ratio compared with those fed a control diet based on 25 percent herring meal, five percent fish oil 20 percent soybean oil meal. The mortal-ity rate for both groups was similar. Taste panel studies indicated that there was no effect of dietary treatment on firmness and flavour of the fish.

Kaneko (1969) reported that 1/3rd of white fishmeal could be replaced by soybean meal with no negative effects on growth of warm

Use of soybean products in aquafeeds: a reviewby T. H.Bhat, M. H.Balkhi and Tufail Banday (Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir)

Figure 1: The chemical composition of Soyabean meal

40 | InternatIonal AquAFeed | January-February 2012

FEATURE

January-February 2012 | InternatIonal AquAFeed | 41

water fishes. Viola (1977) iso-nitrogenously reduced the fishmeal content in the diet of carps containing 25 percent protein supplemented by soybean meal with the addition of amino acids, vitamins and minerals and opined that soybean diet did not induce good growth in carp. Similarly Atack et al (1979) reported poor utilisation of soybean protein by carp when it formed the sole protein source. Gracek (1979) used different qualities of soybean meal to sup-plement ground maize for feeding carp fry and recorded better survival.

No difference in growth was observed when common carp (Cyprinus carpio) were fed either with 45 percent soybean meal (+10 percent fishmeal) or 20 percent soybean meal (+22 percent fishmeal). Other trails however showed that the growth performance and feed efficiency of common carp were reduced when dietary fishmeal was replaced by soybean meals.

There were no differences in performance between extruded full fat soybean meal and oil reconstituted soybean meal (Inghet et al; 1991). A better weight gain was reported when soybean meal was incorporated in the diets of carp fish (Cristoma et al; 1984). Similarly sklyrov et al (1985) successfully used soybean meal in rearing carp fish commercially. It is claimed that soybean meal is deficient in available energy and lysine as well as methionine for carps. Supplementation of soybean meal diets with methionine coated with aldehyde treated caesin significantly improved utilisation of amino acid by common carp (Murai et al; 1982).

Lack of phosphorus rather than the sulphur amino acids may be the cause for poor perform-ance of common carps when 40 percent soy-bean meal diets were fed to them. Addition of 2.0 percent sodium phosphate did not improve their performances (Viola et al; 1986). Kim and Oh (1985) attributed the poor performance of common carp fed with a diet containing 40 percent soybean to lack of phosphorus rather than sulphur and amino acids, since addition of two percent sodium phosphates to soybean meal diet improved their performance to a level obtained with the best commercial feed.

Nour et al (1989) studied the effect of heat treatment on the nutritive value of soybean meal as complete diet for common carp by autoclaving the soybean seeds for 0, 15, 30, or 90 minutes and recorded maximum average daily weight gain with diets containing soybean seeds autoclaved for 30 minutes. Nandeesha et al (1989) incorporated soybean meal in the diets of Catla and indicated the possibility of utilising soybean meal in carp diets.

Keshavapa et al (1990) used soybean flour in the diet of carp fry and recorded better survival. Senappa (1992) studied protein digestibility from soybean-incorporated diets and recorded better digestibility when fed to fingerlings of Catla. Naik (1998) studied the effect of Soya flour and fishmeal based diets in the diet of Catla catla & Labeo rohita and observed a better growth and

survival of carps when reared together and also in combination with fresh water prawn.

Channel cat fish (Ictalurus punctatus) fed on all plant protein diets grew significantly less than fish fed diets containing fishmeal (Lyman et al, 1944). Growth was substantially reduced when menhaden fishmeal was replaced by soybean meal at an isonitrogenous basis (Andrews and Page, 1974). Full fat soybean meal heat treated differently replaced fishmeal at low levels in diets for channel cat fish showed that replacement gave satisfactory results (Saad, 1979).

Growth and feed efficiency of fingerling hybrid tilapia (Oreochromis niloticus) was significantly depressed when soybean meal replaced fishmeal at the optimum level (30 percent) in their diet (Shiau et al, 1988). The growth depression of the hybrid tilapia was reduced when a 30 percent crude protein diet containing soybean meal but by adding two to three percent dicalcium phosphate to the diet, growth rate of tilapia was comparable to the control (Viola et al, 1986). Soybean meal with supplemental methionine could replace up to 67 percent fishmeal in the diets for milk fish (Chanos chanos) (Shiau et al, 1988).

Growth, feed conversion and survival of tiger prawn (Penaeus monodon) juveniles fed two levels of soybean meal under laboratory conditions were lower with higher levels of soybean meal (Piedad, Pascual and Catacutan, 1990). No significant differ-ences in growth and survival could be established when soybean meal at levels from 15- 55 percent replaced par-tially or completely fish meal in the diets for tiger prawns stocked in cages in ponds at 10 to 20 shrimps per square meter (Piedad, Pascual et al, 1991). Lim and Dominy(1991) obtained compara-ble results in feeding Penalus Vannamel with diets containing up to 17 percent of dry extruded full fat soybean meal as a partial replacement for fish protein.

Generally the studies outlined above together with several others indicate that there is an advantage to be gained from using properly processed soybean products for formulating diets for fish due to their better quality protein

and higher dietary energy value in full fat soybean which is more advantageous with cold water fish species because warm water fish (Carp, Catfish etc) can utilise carbohydrates more efficiently. The only recommendation relating to the limit of inclusion of full fat soybean in fish diets is not to exceed the known practical limits relating to fats in general in order to avoid problems of feed preparation and to reduce the risk of high fat levels in the meal.

Recommended Inclusion RatesSoybean may replace animal protein in diets for

aquatic animals to a certain extent. However, with increasing substitution of e.g. fish meal by soybean meal the performance of fish decline. Herbivores may tolerate higher levels of soybean meal than carnivores. It appears that full fat soybean meal is more beneficial for cold-water fish than for warm water species due to the better utilization of the energy from the soybean products. Only properly heat-treated soybean products should be used for aquatic feeds. Furthermore, it is advisable to use only soybean meals processed from dehulled seeds in order to reduce the crude fisher content in the diet. ■

This article originally appeared on

40 | InternatIonal AquAFeed | January-February 2012 January-February 2012 | InternatIonal AquAFeed | 41

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As more of world’s natural fisheries are depleted and demand of fish continues to rise, aquaculture will

continue to grow, thus raising demand for healthy, commercially prepared fish

Mostly, aquaculture relies upon extrusion cooking to produce feeds that are good mix and nutritionally available, but also in a form that is capable of moving through water column very slowly (floating) to be ingested. Thus, the big dependency in aquaculture is selecting ingredients that when extruded will possess just right buoyancy, not migrate nutrients into water, with high palatability for specific fish species.

Fishfeed pellets are prepared either by pressed cut sheets or by Extrusion methods. This article will discuss about Ingredients and Extrusion process for pro-ducing the pellets.

Main ingredients include: 1) Fish & Bone Meal 2) Soy protein (though it is not preferred

by farmers being not easily digestible by many fish species)

3) Wheat 4) Starch 5) Blood Meal

Other ingredients like Vitamins, Minerals and Lipids (Fat Oil) are also added in producing pellets.

FishmealFishmeal is a well-known source of

proteins which is strongly demanded by the animal feeds industry. This is due to its balanced amino acid content, which makes it an ideal feed for many domestic animals.

Moreover, its use to adjust (improve) the amino acid con-tent of other dietary protein sources also contributes to increase demand for fishmeal. As its name points out, fishmeal is derived from captured fish, including whole fish, fish scraps from fillets, and preserves of industries.

Most of the main capture fishery producers devote the main part of this activity to fish meal production. The raw mate-rials used in fish meal manufac-ture come almost entirely from species which are not often used for human consumption (either due their size, or because they are very abundant).

The fishmeal processing system consists of preserving initial fish proteins by means of a controlled dehydration, which extracts around 80 percent of the water and oils contained when fresh from fish.

This leads to the produc-tion of a dry product, easy to preserve and easier to transport than the initial product.

Fresh fish entering the manu-facturing plant is first ground and

then cooked in a continuous heating oven at 90-95 percent, which in-turn coagulates proteins and lose their water-holding capac-ity. The hot mash is then transported to an

by R V Malik, CEO, Malik Engineers, Mumbai, India

Aquaculture: Producing aqua feed pellets

10 | InternatIonal AquAFeed | March-april 2011 March-april 2011 | InternatIonal AquAFeed | 11

F: Feed pellets

endless screw or oil expeller that presses it and squeezes out most of the remaining water and oils.

Pressed fish coming out of the press (press cakes) then cut into smaller portions and placed into a dryer on a steam heated surface. During the drying period, the mash is in constant motion and subject to an air jet that removes all the steam emitted. The dried mash obtained is now called 'fish meal' and contains from 8 to 10 percent of water.

However, if the moisture level is more than 11 -12 percent, there is a risk of the fish meal developing moulds. Generally, antioxidants are added when fish meal is introduced and taken out of the dryer, and by so doing ensuring the stability of the oils remaining within the fish meal.

Soy proteinNot all fish species have easy digestibility

of soy protein, primarily due to increased carbohydrate content fraction. It is usually used as supportive additive with other eas-ily digestible protein like fish meal which is rich in fish proteins.

Bean processing consists essentially of extracting the oil so as to concentrate the proteins. This process provides a very important by-product, namely soya oil, which is widely used as a raw material and oil for human consumption. This proc-ess also contributes to the elimination of certain anti-nutritional factors present in the raw bean.

The first step in processing involves the removal of the shell (cellulose) from the grain. The ‘bare’ beans are then heated, on the one hand to reduce the activity of certain enzymes, and on the other to break the cellulose strands and facilitate the following steps. The heated beans are then mashed to form thin paste-like slices, which further facilitates the destruction of the cellulose structure and oil extraction.

The product, now termed ‘whole soya cake’, still contains its oil and has around 40 percent protein, and as such is sold directly for animal feeding.

Next, the oil can be extracted from the whole cake by means of a solvent (such as hexane). After total evaporation of the solvent, there remains the solvent extracted soya cake, which in turn is widely used for animal feeding, and contains 45 - 50 percent protein.

BloodmealAbattoirs or slaughterhouses produce

many important by-products, such as

blood and bones, etc which are often difficult to commercialize.

N o w a d a y s , however, these by-products constitute the basic raw mate-rial of the bone and blood meals widely used in industry for animal feeding.

Cons iderab le amounts of blood are produced by abattoirs, and this product is usu-ally transported to drying ovens and converted into blood meal. Blood from differ-ent origins such as, sheep, goat, and poultry are usually stored and proc-essed separately. However, so as to comply with basic sanitary measures, it is generally com-pulsory to store blood within cool-ing chambers and to ensure that the level of bacteria is kept within pre-scribed maximum limits.

The manufacture of bloodmeal

Fresh blood is kept cool at the factory, and sizeable particles filtered and the blood mass stirred so as to separate the fibrillar phase from the liquid mass. The fibrin is then heated up to coagulation and the coagulated mass divided and dried through a hot air stream (that is by spray drying). This method is particu-


F: Feed pellets

Quality control and testing ofraw materials

Product development and recipe optimization

Small-scale production

Quick change of test conditions

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Formulation of fishfeedAs we have seen, feed formulators can

resort to a wide assortment of raw materi-als to make up a food mixture so as to meet the nutritional requirements of the fish for energy, amino acids, fatty acids, carbohydrates, vitamins and minerals.

These raw materials are generally used in flour or liquid form, and will have to undergo binding by means of a technologi-cal process to obtain a food mixture in the form of dry pellets, which are easy to use and preserve.

As a guide, salt water marine aquaculture is dependant upon high levels of proteins with high digestibility. The fresh water aqua-culture relies upon more carbohydrates, that is high levels of grains coupled with modest to high quality proteins, minerals, vitamins with little or no fiber.

The first factor to be considered for feed formulation is the total energy and protein/energy ratio of the final product. After this, the protein content must be cal-culated according to the amino acid balance desired, and the lipids included to satisfy the best fatty acid profile for the species concerned and the energy level desired. All this must be considered taking into account the vitamin and mineral requirements of the cultured species.

This formulation is not easily reached and so computerised linear programming techniques must be used. Furthermore, it is also necessary, after covering all the nutritional requirements of the species within the formula to also produce a range of tasty feeds of different pellet sizes for the different age classes.

Manufacturing stages

- StorageThe raw materials coming into the feed

manufacturing plant are generally stored in silos with an ideal height calculated so as to allow the raw material flow to be conveyed downwards, during the manufacturing proc-ess, until the final product is produced. This is in order to avoid having to pull the prod-ucts up by vertical conveyors that usually cause breaks and dust in the final product.

- GrindingGrinding raw materials reduces particle

size and increases ingredient surface area, thus facilitating mixing, pelleting and digest-ibility. The most commonly used grinders are hammer-mills, for fish feed manufacture, as plate-grinders do not generally produce fine enough ground materials.

The Extrusion cooking process utilizes

LipidsFish oils are co-products of the fish-

meal industry. Their nutritional charac-teristics regarding fatty acids make them indispensable for fish feed manufacture, and in particular their characteristic high content of n-3 unsaturated fatty acids (first double bond linkage in posi-tion 3), which are essential for a well balanced food formula for carnivorous fish species.

A large amount of fish oil arising from fish meal manufactures is re-processed in specialized facilities for diverse purposes; part of it being hydrogenated and mixed with other lipids, and transformed into mar-garine, mayonnaise and bakery compounds, and the other part used directly by the feed industry.

MineralsMinerals are measured as ash in the

recipe. Though they serve no functionality in extrusion (on the contrary their abrasive nature will accelerate wear and tear of working parts in extruder), these are usu-ally added in proportions < 5 percent. They include phosphorous, calcium (from calcium carbonate or ground lime stone), sodium chloride (salt), magnesium, potassium, etc.

Vitamins:They can be water soluble or soil solu-

ble. Vitamin B and C are water soluble, A, D, E, and K are fat soluble. They are added in proportions < 0.5-0.6 percent in diet, but due to harsh processing conditions inside the extruder, these get destroyed, hence they are added well in excess of minimum requirements.

Apart from above, the feed may contain, flavors/aromas, antioxidant (preservative) and antimicrobials, dyes & pigments (for human appeal and dis-tinction, rather than for fish itself), etc. It is important to use certified ingredi-ents that does not affect health of fish. Pigments are usually added as a coating step, to minimize losses during harsh extrusion processing conditions.

larly gentle (spraying a product in a hot air-stream) and does not denature the proteins because the water evaporation cools down the hot air very quickly, thereby preventing overheating.

Wheat flourWheat is one of the most important

cereals worldwide, and is used for making bread and for many other produces. It is also an essential raw material for livestock feeding, including fish.

Wheat in fish feedingStarch products, especially wheat, are fre-

quently used as binders for the manufacture of pellets; the gelatinizing property of starch when water-heated being useful for this purpose as the starch absorbs water and forms a gel.

Moreover, when starch is gelatinized its digestibility improves considerably. Various starch types (wheat, barley, rice, maize or potatoes) can gelatinize but each one will have its own characteristics.

In addition, all three starch types gener-ally have the capacity to form a stable structure when subjected from high to low pressure during the extrusion process.

It is this property that is used for feeds that must have a high lipid content, during the extrusion process the starch forms a cell structure with alveoli that can then be filled with oil instead of air and/or steam.

For carnivorous fish feeding purposes the starch must be considered as a sup-porting structure that gives the pellets their texture and together with the other dietary ingredients allows the formation of a binded diet.

However, since the natural feeding habits and foods of seabass and/or seabream usually contain very small proportions of carbohydrates (ca. three percent glyco-gen, animal starch - glucose polymer). If excessive quantities of digestible starch are provided in the feed this may result in the accumulation of excess liver glycogen, which in turn may trigger a liver dysfunction.


F: Feed pellets

as ‘expanded feed’, is also marketed by some manufacturers.

The main difference between a pressed and an extruded feed is the cooking of the feedstuff in the case of extrusion, with the added mechanical and biological advantages previously described, especially with regard to starch gelatinization

Extruded Feeds:The Extruder can be described as a

Bio-Reactor with (mostly) a single, multiple-flighted screw (rotor) rotating at high speed inside a stationery hollow tube (stator).

The raw materials fall from top at one end on the rotating screw which has multiple flights and varying pitches along its length. The barrel (tube) is externally heated/cooled by steam and cold water externally around. Due to this arrangement, a high pressure of around 40-70 bars (Kg/cm2) is developed on the ingredients, temperature of ingredients varies from 110 C to 160 C, which ensures cooking of ingre-dients into plastic mass which is extruded out of multiple die openings/orifices and cut to produce porous pellets for fish feed.

Pre-Extrusion: Dry ingredients after having been mixed & ground thoroughly in desired proportions, are usually transport-ed to the Single screw Extruder (Cooker) provided with a Pre-conditioner at top.

The Feed Delivery System: It consists of a “Live Hopper” or Bin with a horizontal conveying screw to convey dry ingredients to the Preconditioner from above. The Bin is provided with device which avoids bridg-ing of material (since raw ingredients have low bulk density and poor flow through a normal Hopper) and ensures continuous flow of materials to the Preconditioner below, hence the name “live” bottom bin. It should hold adequate volume to support the extruder operation for minimum 5-8 minutes, as a buffer time for the operator and auto control network to respond

force, position themselves form-ing a star on the rotor and split the incom-ing feedstuff apart, which is then forced by depression through a metal grid composed of appropriately sized meshes.

- MixingThe ground

ingredients must be mixed accord-ing to the desired proportions to obtain a homoge-

neous mixture. If the grinding process is correctly developed, the particles are homogeneous in size and the mixture produces pellets which statistically have the same formulation.

Generally, the dry ingredients (flours) are first mixed, followed by the liquid components. Continuous mixers are designed so that the feedstuff moves along the mixer as it mixes. There are many different types of mixers, including horizontal band-mixers, vertical mixers, conical screw-mixers, and turbine mixers, etc.

During this mixing process, the vitamin ‘premix’, the binding agents and other additives are added; they must in turn con-tribute to one or other particular desired quality of the pellets during the pelleting process.

- PelletingTwo different types of pellets are gener-

ally prepared for aquafeeds, namely pressed and extruded pellets. A third type, designed

wide variety of ingredients that can have varying particle sizes. It is desirable, but not necessary that all ingredients be of uniform particle sizes, to prevent segregation during mixing and transport prior to extrusion.

Uniform particle size of ingredients pro-motes better mixing and uniform moisture uptake by all particles during the precondi-tioning step.

If the particle size of raw ingredients is too large, the final product may contain particles which are improperly cooked, which degrade product appearance and palatability.

Also, if particle size is larger than die orifice used at extruder discharge, it may cause plugging of some orifices affecting capacity and appearance. As rule of thumb, it is necessary to maintain size of raw ingredients one third of the die opening die. Hence the need of size reduction equip-ment and sifting.

In hammer-mills, the grinding chamber consists of a series of mobile hammers on a rotor. The hammers, by centrifugal


F: Feed pellets

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MIXING CONDITIONING PELLETING EXTRUSION COATING COOLING

“Wet Extruder” since feed materials con-tain around 25 to 30 percent moisture (water). Both screw and the barrel are made up as separate segments so that individual components could be replaced when worn. Multiple flighted, varying pitch screw elements are usually employed to provide cooking and forward convey-

ing of feed materials. The Volumetric capacity of screw is highest at Feed zone to account of low bulk density of ingredients. However, it reduces (lower pitch) towards the die, which causes compression and cooking of feed mate-rial. The final discharge end of screw is usu-ally Conical to generate high pressure and attain maximum expansion of pellet when emerging

from die opening. The barrel heads are provided with Steam Heating and water cooling Jackets around, for heating or cooling, as per process demand. The proc-ess temperature is held from 110 C to 160 C gradient from Feeding Zone to Final Cooking Zone. Maximum convey-ance & mechanical shear of material is ensured by action of multiple flighted screw elements and spirally grooved bar-rel segments. Water present inside the mixture is held as steam at high tem-perature and pressure. However, as soon as the cooked mass emerges out of die openings pressure drops to atmospheric

- ExtrusionUsually single screw Extruders with sin-

gle barrel and screw is used for cooking the preconditioned ingredients, but twin screw extruders are also used. The latter have limited use because of high initial capital costs compared to single screw extruder.

The action of the Extruder allows the free flowing ingredients to bond to each other and remain in pellet form after exiting from shaping (pelleting) die. It does this by the action of rotating screw or spiral inside a stationery barrel by generating high mechanical shear and raised temperature on feed materials.

Extruders for Fish Feed production have Mechanical Energy Input levels between 20-40 Kw-hr/ton of produce. Their screws run between 400-1000 RPM depending on sizes. Output capacities range between 1 t to 20 t per hour.

The Extruder usually employed is

and allow recharging the bin from top. The screw is provided with variable speed motor to properly adjust the flow as per production capacity of the Extruder.

Preconditioning: This step ensures the dry ingredients are constantly added with moisture (water) in desired proportions (25-30%) and steam is also added, at 5-6 bar, for pre-cooking the wet ingredients. As the ingre-dients move forward towards the Extruder feed opening, they are held at temperature of approximately 100 C and atmospheric pres-sure. Preconditioning makes the ingredients soft by precooking and it reduces energy require-ment in the Extruder. If Lipids are to be added, their proportion is lim-ited from 5-7 percent in this stage.

Conventional Preconditioners had only one tank and single agitator, but modern preconditioners have special oval tanks with two agitating shafts with adjustable beaters to control residence time inside the tank. Two agitators result in the better mixing of dry and liquid ingredients. Longer retention time approximately 2-2 ½ minutes are desirable before feeding into the Extruder. Usually lipids are added not more than 5-7 percent by weight here, since it leads to excessive slippages inside the Extruder and poor mixing & expansion/texture of final pellets.

Table 1:

FeeD a FeeD B Difference

(1) Growth 1 1.1 10%

2) Conversion rate 2 2 0%

(3) Feed price / kg 5 6 +20%

(4) Selling price of fish 50 50 0%

(5) Feed expenditure for 1 kg of fish produced (2) X (3) 10 12 +20%

(6) Profit from fish sales (1) X (4) 50 55 +l 0%

(7) Gross margin for feed item (6) - (5) 40 43 +7.5%

"As more of world’s natural fisheries are depleted and demand of fish continues to rise, aquaculture will continue to grow, thus raising demand for healthy, commercially prepared fish"


F: Feed pellets

applied through bed of pellets to lower the temperature.

Cooling is important, since if packed in hot state, moisture will condense in the packing, wetting the outer surface of the pellets, allowing mold growth. It is desir-able to cool down within 10 C of ambient air tempt. So that problem of condensation in packing doesn’t occur.

- BaggingBagging usually produces different

types of feed presentations within the same factory, namely either small bags (20 or 25 kg) on pallets covered with a plastic film, or big-bags (500 or 1000 kg) in bulk.

Viability of Extrusion process

It follows from the higher tempera-tures and pressures used during extrusion processing that investment and energy costs will be higher than those of conven-tional pressed feeds. Despite this however, the use of extruded feeds may be more profitable.

Following Table (illustration) summa-rizes the theoretical results obtained with fish fed a pressed (A) or extruded (B) feed.

Table showing Justification for Extrusion Over Press Feed production method for Fish Feed.

It is clear from the example given that despite the fact that the price of the extruded feed is 20 percent higher, the feed which provides 10 percent additional growth provides a 7.5 percent additional gross margin.

time of products should be carefully adjusted to attain properly dried product that can absorb maximum fats and coat-ings in the Coating step.

- SiftingThe mechanical manufacturing processes

inevitably results in shocks and scorching that partially crumble the pellets at their surface and cause various breaks and dust that must be eliminated. This is achieved by sifting, a process that is generally applied at least twice before the final condition-ing (sifting after drying and after coating/cooling).

- CoatingThe pellets emerging from the pel-

leting presses or extruders do not generally contain more than 7 to 10 percent lipid. To achieve higher dietary lipid levels (20-27%), coating is neces-sary with the appropriate oils, generally using heat. In the same manner, certain heat sensitive vitamins and/or drugs that would not normally withstand the harsh extrusion processes (thermo labile products) can also be added later during the coating process. These ingredients are usually added through spray nozzles fed through dosing pumps which accurately control the weights deposited. They can be vacuum assisted for still more good results.

The Expansion that occurs as a result of extrusion processing makes the product porous with low bulk density and air pockets, so that more oil is absorbed during the spray coating process. Fats could be added in the form of Animal fats, Fish Oil or Vegetable Oil.

- CoolingOn completion of the coating process

(generally undertaken with heated mate-rial) the pellets are then cooled and sieved before the final conditioning; cooling occur-ring in a cool-air flow generated by a cooling-machine. Again, this machine usually provides continuous flow of product on perforated steel belts, while cooling air is

and the product expands or “puffs”, being cut continuously by Rotating Die Knives working against the die Face, giving the pellet the specific rounded shape for extruded pellets.

Retention time inside Extruder is from 100-180 seconds, which ensures 70-85 per-cent starch gelatinization and production of good shape and density.

The above Extruder produces Floating Pellets with low bulk density, e.g 350-450g/l that are classified as “Floating” and sink very slowly into water column. Most Extruders have an arrangement, whereby the water vapour present in the mix is released by a vent opening on the barrel so that high den-sity pellets or sinking pellets are produced for certain species of fish.

The following parameters will con-trol the final pellet density: 1. Initial moisture content (usually 25-30 percent on wet basis). 2. Process temperature. 3. Extruder back pressure. 4. Extruder RPM (residence time). 4. Drying condi-tions and temperature. 5. Quantity of Fats, vitamins & minerals applied post extrusion.

- DryingWhen added to Extruder, the ingre-

dients contain around 25-30 percent moisture (wet basis). Extrusion process evaporates approx. 4-7 percent moisture thus still retaining considerable moisture inside the pellets. After the pelleting process, the pellets usually have a high moisture content (17 to 22%) that must be quickly reduced to avoid spoilage. This is usually achieved by using a hot-air drier, which lowers the moisture level to between 8 and 10 percent depending upon the manufacturing process.

Continuous Belt Dryers are com-monly employed that provide heated air to remove excess moisture from wet product, as it travels on multiple decks of perforated steel belting. Since the Drying process is critical and determines the quality of pellets, it needs to be carefully monitored and controlled. The Air Temperature, Humidity and Residence

ARCHIVEEvery featurethatappears in InternationalAquafeedmagazine,willalsoappear inouronlinearchive.Pleasevisit:

http://www.aquafeed.co.uk/archive.php

Note:TheauthorisCEOMalikEngineers,Mumbai,whichmanufacturesawiderangeofextrudersforfoodprocessingandaqua/[email protected]:+919821676012,+912228830751,+912502390839

16 | InternatIonal AquAFeed | March-april 2011

F: Feed pellets

Gilthead sea bream pro-duction in Mediterranean countries increased from 30,000 tons in 1996 to

90,000 tons in 2005,which mean that sale prices dropped considerably, from 6.6€/kg in 1996 to 5€/kg in 2005, with an historic minimum of 4€/kg in 2002 (APROMAR, 2006). To maintain the profitability of gilthead sea bream farms, cutting production costs is nec-

essary, mainly through feeding, which represents between 38 and 45% of operational costs (Lisac & Muir, 2000 and Merinero et al., 2005).

Reductions in feeding costs can be obtained by optimizing feeding strate-gies, nutrient levels in diets, and by using vegetable sources as substitutes for fish oil and fishmeal. This aspect is also very important to improve the sustainability of

aquaculture, as it would reduce depend-ence on fish sources (Martinez-Llorens et al., 2009).

In the last decade, the increasing demand, price and world supply fluctuations of fishmeal (FM) has emphasized the need to look for alternative protein sources in aquafeeds. Some plant ingredients have been studied in gilthead sea bream (lupin seed meal, extruded peas and rapeseed meal) but Poaceae and Fabaceae seeds

and their by- products, among which corn gluten and soybean meal, in par-ticular, are widely used in fish nutrition because of their high protein content (40-60%), low cost and relative wide-spread availability. Therefore, soybean meal being the most nutritive and it is used as the major protein source in many fish diets. Partial or even total replacement of dietary fishmeal by soybean meal protein sources had suc-cessfully accomplished with tilapia diets (Fagbenro and Davies, 2002). Some studies with gilthead sea bream have shown that partial replacement of FM by PPs is possible (Robaina, et al., 1995; Hassanen, 1997a, b; 1998; Kissil, et al., 2000; Sitja-Bobadilla et al., 2005 and Martinez-Llorens et al., 2009). Studies with sea bass have also reported some success to partial replacing of FM by PPs (Lanari, 2005 and Tibaldi, et al., 2006). Studies of using corn gluten to feed carnivorous fish (sea bream) are very limited; therefore, the scope of

Evaluation of Fishmeal Substitution with selected Plant Protein Sources on Growth Performance and Body Composition of gilthead sea bream* Fingerlingsby Abd Elhamid Eid* ,Badiaa Abd Elfattah*, Khaled Mohamed**Department of Animal & Fish Production, Fac. of Agric.Suez Canal Univ. Ismailia 41522, Egypt

*Sparus aurata

Table 1: Composition of the experimental diets

Ingredients (g/100g)*Diet

FM PPs/25 PPs/50 PPs/75 PPs/100

Fish meal (CP 68%) 63 47.24 31.52 15.78 -Corn gluten meal (62%) - 9 20 45 62

Soybean meal (44%) - 13.7 24 13 15Yellow corn 21.5 14.30 8.20 8.90 5.05

Fish oil+ Soya oil (1:1) 1** 12 12 12 12 12L-Lysine -- 0.26 0.62 1.69 2.32

DL- Methionine -- -- 0.16 0.13 0.13Vit & Min mix2 3 3 3 3 3

Cr2O33 0.5 0.5 0.5 0.5 0.5

Total 100 100 100 100 100

1- Mixture of fish oil and soybean oil (1:1 w/w).

2- Each Kg vitamin & mineral mixture premix contained Vitamin A, 4.8 million IU, D3, 0.8 million IU; E, 4 g; K, 0.8 g; B1, 0.4 g; Riboflavin, 1.6 g; B6, 0.6 g, B12, 4 mg; Pantothenic acid, 4 g; Nicotinic acid, 8 g; Folic acid, 0.4 g Biotin,20 mg, Mn, 22 g; Zn, 22 g; Fe, 12 g; Cu, 4 g; I, 0.4 g, Selenium, 0.4 g and Co, 4.8 mg.

3- Cr2O3: Chromic Oxide

* obtained from the local market.


F: Process

the present study was to evaluate the effect of partial or complete replace-ment of fishmeal with increasing levels of plant protein origin like corn gluten and soybean meal on growth performance, feed utilization, body composition and cost production of sea bream fingerlings’ diets.

Experimental protocolDiet preparation - Five isocaloric and isonitrogenous diets were formu-lated based on Fishmeal as the only animal protein source or a mixture of PPs (Corn gluten and Soybean meal) as plant protein sources (Table 1). The diets formulated to be almost containing 45% crude protein by replacing 25, 50, 75 and 100% of the FM (fishmeal protein) in control diet. Crystalline amino acids (L-lysine and DL-methionine) were added to diets PPs 25, 50, 75 and PPs100% to become similar to control diets. Fish oil and soybean oil were added as dietary lipid sources (Table 1). The diets were pelleted using a small catering grinder with a 1.5 mm diameter and kept frozen until the experiment was started. During the growth period (120 days), each diet was randomly allocated to triplicate tanks of fish. Feed was offered by hand at two meals / day (8:00h and 15:00) at 3% of body weight daily and the amount of diets were readjusted after each weighing.

Experimental design - Sea bream fingerlings were obtained from a private fish farm in Damietta governorate. Fish were acclimated to laboratory conditions for 2 weeks before being randomly distributed into fiberglass tank of 300-L water capacity each, in Ashtom Elgamel, Port-Said governorate. The water was obtained from channel comes from Mediterranean sea. Fish of 10±0.2 g initial body weight were distributed into 15 experi-mental tanks in triplicate groups of 50 fish each. The photoperiod was regulated to be 12h light: 12h dark. Water temperature was maintained at 25ºC by a 250- watt immersion heater with thermostat. Water temperature and dissolved oxygen were recorded daily (by Metteler Toledo, model 128.s/No1242), other water quality parameters including pH and ammonia were measured every two days by pH meter (Orion model 720A, s/No 13062) and ammonia meter (Hanna ammonia meter). Water salinity was 34ppt. The average water quality criteria of all tanks are presented in Table 3. All fish in each tank were weighed every 10 days.

Experimental methodology - The tested diets and faeces were analyzed for crude protein (CP %), ether extract (EE %), crude fiber (CF %), ash (%) and moisture while whole body composition of sea bream fish samples was also analyzed except for crude fiber (CF %) according to the procedures d e s c r i b e d by A.O.A.C. (1995) as shown in Table 2 and Table 5. The nitrogen f r e e - e x t r a c t (NFE %) was calculated by d i f f e r e n c e . Blood samples were col-lected using h e p a r i n i z e d syringes from caudal vein of the experimen-tal fish at the t e r m i n a t i o n of the experi-ment. Blood was centrifuged at 3000rpm for 5 minutes to allow separa-tion of plasma which was subjected to d e t e r m i n a -tion of plasma total protein ( A r m s t r o n g and Carr, 1964)

and plasma albumin (Doumas, et al., 1977). Apparent protein digestibility was deter-mined using the method of Furukawa and Tasukahara (1966). For determination of protein digestibility the diets and faeces were collected during the last 15 days of the experimental period. Any uneaten feed

Table 2: Proximate analysis of the experimental diets (% as fed)

Chemical analysisDiet


Moisture 8.50 8.00 8.30 8.70 8.80

Crude protein* 44.71 45.00 45.1 45.1 45.60

Crude fat 17.56 16.42 15.32 14.48 13.32

Crude fiber 1.14 1.95 2.57 2.00 2.18

Crude ash 9.30 8.00 6.55 4.14 2.33

Nitrogen free extract 18.79 20.63 22.16 25.58 27.77

Gross Energy (kcal/100gm) 1 495.15 493.59 490.06 496.18 497.05

P/E Ratio (mg protein/Kcal) 2 90.30 91.20 92.00 90.90 91.70

1. Based on 5.64 Kcal/g protein, 9.44 Kcal/g fat and 4.11 Kcal/g carbohydrate (NRC, 1993).

2. Protein/Energy Ratio (mg Protein/Kcal).

A new generation of omega-3 lipids with a broader spectrum of health bene� ts.

- High DHA contents, preferably in easily digestible and highly bio available form for aquaculture use.

- Numerous bene� ts on improving the immune response, better weight gain and physical conditions of land animals.

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F: Process

bream diets with no significant differences (P≥0.05) in growth performance compared to the control (Table 4). This conclusion is in agreement with Gomes et al (1995a & b) for rainbow trout. These workers reported that replacement of fishmeal by plant protein sources had no adverse effects on growth. The optimal rate of sub-stitution found in the present research was closed with Lanari (2005), he reported that soybean meal can substitute up to 25% of total protein of the sea bass diets without any negative effect on growth performance. Higher value than reported in the present study was reported by Gallagher (1994) in diets for hybrid striped bass, where soybean meal substituted 44% of fishmeal without evidencing a negative

effect on the feed intake and he also report-ed that up to 75% of fishmeal protein can be replaced with soybean meal. M o r e o v e r , Sitja-Bobadilla et al., (2005) reported that up to 75% of fishmeal pro-tein can be replaced by plant protein sources for juvenile sea bream, which also is in agree-ment with the present study for sea bream fingerlings. In the recent years, signifi-cant amount of research has been con-ducted on the replacement of FM by different PP sources.

In European sea bass ( D . l a b r a x ) (Kaushik et al., 2004) and Gilthead sea bream ( S . a u r a t a ) (Pereira and

in an oven at 60oC and kept in airtight containers for subsequent chemical analysis.

Statistical analysis - All data of growth performance, body composition and blood parameters were analyzed by one-way analysis of variance (ANOVA) using the general linear models procedure of statistical analysis system (SAS) version 8.02, (1998). Duncan's multiple range test (Duncan, 1955) was used to resolve dif-ferences among treatment means at 5% significant level using the following model.

Results & discussionThe present study indicates that PPs

(corn gluten and soybean meal) can replace 25% to 50% of fishmeal protein in sea

or faeces from each tank was carefully removed by siphoning about 30 min after the last feeding. Faeces were collected by siphoning separately from each repli-cate tank before feeding in the morning. Collected faeces were then filtered, dried

Table 3: Average water quality parameters in the experimental tanks used in the study.

Parameter Means ± SD

Temperature (ºC) 25 ±1

Oxygen (mg/L) 5.4 ±1

Ammonia (NH3, mg/L) 0.011± 0.0001

pH 7.1 ± 0.10

Salinity (ppt) 34.0 ± 0.4

Table 4: Growth performance and feed utilization of sea bream (S. aurata) fed the experimental diets

ParametersDiet

FM PPs 25 PPs50 PPs75 PPs100

Average Initial body weight (g) 10.1±0.05 10.2±0.25 10.3±0.10 10.1±0.10 10.0±0.23

Average Final body weight (g) 102.6 a ±2.2 101.3 a ±0.3 97.7 b ±0.20 85.2 c ±0.2 78.9 d ±0.20

Average Weight gain (g) 92.5 a ±1.1 91.1 a ±1.2 87.4 b ±0.9 75.1c±0.10 68.9 d±1.10

SGR (% / d)1 1.93 a ±0.02 1.91 a ±0.01 1.87 a ±0.02 1.78 b ±0.09 1.72 b ±0.01

Feed intake (g) 151.93 a ±0.4

152.51 a ±0.2a

153.15 a ±0.10

159.62 b ±0.2

159.30 b ±0.10

Feed conversion ratio (FCR2 1.64 d ±0.10 1.67 d±0.1 1.75 c ±0.10 2.13 b ±0.1 2.31 a ±0.20

Protein efficiency ratio3 1.35 a ±0.01 1.32 a ±0.02 1.27 a ±0.01 1.04 b ±0.10 0.95 b ±0.20

Feed efficiency4 0.61 a ±0.1 0.60 a ±0.10 0.57 a ±0.10 0.47 b±0.10 0.43b ±0.12

HSI (%)5 3.2 a ±0.1 2.97 a ±0.1 2.93 a ±0.12 2.71b ±0.01 2.56 c ±0.12

Apparent Protein Digestibility (APD)6 88.25 a ±0.3 87.39 a ±0.2 86.09 a ±0.1 73.16 b±0.2 65.32 c ±0.1

PTP (g/dl)7 5.21±0.10 5.20±0.12 5.15±0.10 5.03±0.12 5.01±0.10

PA (g/dl)8 2.15±0.11 2.17±0.11 2.17± 0.12 2.07±0.02 2.08±0.08

PTG (g/dl)9 3.06±.0.12 3.03±0.10 2.98±0.11 2.96±0.09 2.93±0.01

Survival rate (%)10 100 100 98 96 94

Values in the same row with a common superscript letter are not significantly different (P≥0.05).

Specific growth rate = (100 x [(Ln final wt (g) – (Ln initial wt (g) / days.]

Feed conversion ratio (FCR) = feed intake (g) / body weight gain (g).

Protein efficiency ratio (PER) = gain in weight (g) / protein intake (g).

Feed efficiency = body weight gain (g) / feed intake (g).

Hepato-somatic index = 100 x liver wt / fish wt.

6 - Apparent protein digestibility, APD (%)

7 - Plasma Total Protein, PTP (g/dl)

8 - Plasma albumin, PA (g/dl)

9 - Plasma total globulins= plasma total protein- plasma albumin, PTG (g/dl)

10 - Survival rate =No of survive fish/total No. of fish at the beginning X100


F: Process

fish. In fish, protein digestibility is generally high ranging from 75% to 95% and the apparent digestible coefficient of proteins from fishmeal is often higher than 90% in salmonids (NRC, 1993). Soybean meal contains various anti-nutritional factors such as the anti-trypsin and an anti chimotrypsin factors, lectins, oligosaccharides and a low level of methionine. Corn gluten has also a low level of amino acid lysine reduces the protein digest-

ibility and amino acid availability of these plant protein ingredients.

Corn gluten meal (CGM) is considered to have a good digestibility (NRC, 1993). Diets containing 20% of CGM meal had a very good digestibility, in accordance with the results of Morales et al.(1994) and Gomes et al. (1995 a) in rainbow trout fed diets containing about 20% corn gluten meal. In contrast, apparent digest-ible coefficient of diets with high levels of plant proteins was very low. In common carp, Pongmaneerat et al. (1993) observed that the apparent protein digestibility

These results of feed utilization related to apparent protein digestibility of diets used in the experiment which showed worst feed utilization of sea bream fed on diets containing high mixture of PPs (corn gluten meal and soybean meal) was possibly due to the low biological value of such based diets, which are in agreement with Robaina, et al.,( 1995), Boonyaratpalin et al.,(1998), Regost et al.,(1999), Lanari (2005), Sitja-Bobadilla et al. (2005), and Tibaldi, et al.,(2006).

Regarding to feed digestibility (Table 4), several investigations were conducted to evaluate PPs and their digestibility by

Oliva-Teles, 2003 and Gómez-Requeni et al., 2004); short-term studies have shown that at least 60-75% of FM can be replaced by mixture of PPs without compromising growth performance for these species. In the present study, the effects of FM replace-ment were studied on growth performance and feed utilization. This scenario, a high level of FM replacement by (50-75PPs %) produced a slight reduction in growth performance. Concerning the results of feed utilization in terms of FCR, PER and FE in the present study, the same trend was showed with growth performance.

Table 5: Whole body composition (% fresh weight ) of see bream (S. aurata) fingerlings fed the experimental diets

Chemical analysis InitialFinal


Moisture 70.50 59.91 a 60.44 a 60.75 a 63.50 b 64.33 b

Crude protein 14.25 17.56 a 17.50 a 17.56 a 17.34 b 16.90 b

Crude fat 10.5 15.62 a 15.70 a 15.77 a 14.00 b 13.90 b

Crude ash 4.75 6.91a 6.36 a 5.92 b 5.16 c 4.87 d

Values in the same row with a common superscript letter are not significantly different (P≥0.05)

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Boonyaratpalin,M., Suraneiranat,P., and

Tunpibal,T..(1998). Replacement of fishmeal

with various types of soybean products in

diets for the Asian seabass, Lates calcarife,

Aquaculture,161: 67-78.

Dias, J., Alvarez, M.J., Diez, A., Arzel, J., Corraze, G.,

Bautista, J.M.and Kaushik, S.J. (1998).

Regulation of hepati lipogenesis by dietary

proteinrenergy in juvenile European seabass

Dicentrarchus labrax .Aquaculture 161 : 169–186.

Doumas, B. T., Waston, W. and Biggs, H. H., (1977).

Albumin standards and the measurements of

Serum albumin with Bromocresol Green. Clinical

Chemistry Acta, 31: 87-96.

Eid, and Mohamed., K.,(2007).Effect of fishmeal substitution by plant protein sources on growth performance of seabass fingerlings (Dicentrarchus labrax). Agricultural Research Journal, Suez Canal University, 7 (3): 35-39.

Fagbenro, O.A. and Davies, S.J. (2002). Use of oilseed meals as fishmeal replacer in tilapia diets. Proceeding of the fifth international symposium on tilapia aquaculture. Rio de Janeiro– RJ, Brazil 1: 145-153.

Gallagher, M.L. (1994). The use of soybean meal as a replacement for fishmeal in diets for hybrid striped bass (M. saxatiles X M. chroy sops) Aquaculture, 126 (1-2) : 119-127.

Gomes, E. F, Rema, P. and Kaushik, S. (1995a). Replacement of fishmeal by plant proteins in the diet of rainbow trout (O. mykiss) digestibility and growth performance. Aquaculture, 130: 177-186.

Gomes, E. F, Rema, P. and Kaushik, S. (1995b). Replacement of fishmeal by plant proteins in diets for rainbow trout (O. Mykiss) : Effect of the quality of the fishmeal based control diets on digestibility and nutrient balances. Water Science and Technology, 31: 205-211.

Gomez-Requeni, P., Mingarro, M., Calduch-Giner, J.A., Medale, F., Martin, S.A.M., Houlihan, D.F., Kaushik, S., and Perez-Sanchez, J., (2004). Protein growth performance, amino acid utilization and somatotropic axis responsiveness to fishmeal replacement by plant protein sources in gilthead sea bream (Sparus aurata). Aquaculture, 232: 493-510.

Hassanen, G.D.I. (1997a). Nutritional value of some unconventional proteins in practical diets for sea bass (D. labrax) fingerlings. Egyptian J. Nutrition and Feeds,1(special Issue ):335-348.

Hassanen, G.D.I. (1997b). Effect of diet composition and protein level on growth, body composition and cost of production of gilthead sea bream (Sparus aurata). Egyptian .J. Aquat. Biol & Fish., 2: 1-18.

et al.(2006) and Sampaio-Oliveira and Cyrino (2008) for sea bass D. labrax and Peres and Oliva-Teles (2009) for sea bream S. aurata.

Calculation of the economical effi-ciency of the tested diets was based on the costs of feed because the other costs were equal for all studied treatments.

As described in Table 6 feed costs (L.E) were the highest for the fishmeal diet and gradually decreased with increasing the replacing levels of plant protein sources. These results indicate that incorporation of PPs in sea bream diets reduced the total feed costs.

However, high replacing levels of fishmeal by PP (75 and 100%PP) adversely affected all the growth and feed utilization parameters (Table 4), but the incorporation of PPs in sea bream diets seemed to be economic as incorporation of PPs in the diets sharply reduced feed costs by 13.71, 27.29, 39.64 and 52.44% for 25PPs, 50PPs, 75PPs and 100%, respectively. The reduction of feed costs was easily observed for the feed costs per Kg weight gain which decreased with increasing incorporation levels of PPs in agreement with Soltan (2005) for Nile tilapia and Eid and Mohamed (2007) for sea bass fingerlings.

ReferencesAPROMAR., (2006). Asociacio´ n Empresarial de Productores de Cultivos Marinos de Espan, La

Acuicultura Marina de Peces en ,Espan˜a. Informes anuales. Ca´ diz, Spain, 56 pp.

Ballestrazi, R., Lanari, D., D’Agaro, E., and Mion, A., (1994). The effect of dietary protein level and source on growth, body composition, total ammonia and reactive phosphate excretion of growing sea bass Dicentrarchus labrax . Aquaculture, 127: 197–206. M.

had to be near 94% in a diet without fishmeal (corn gluten meal, soybean and meat meal).

Results of apparent protein digest-ibility in the present study recorded that the dietary inclusion of high levels of corn gluten and soybean meal in replace-ment of fishmeal led to a significant decrease in protein digestibility which are in agreement with Lanari (2005), Tibaldi et al. (2006) and Sampaio-Oliveira and Cyrino (2008). The value of hepato-somatic index was found to be similar to that reported for sea bass by Ballestrazi et al., (1994) and Dias et a. , (1998),

they reported that the values of HSI were 2–3% or above. Effect of the experimental diets on hepato–somatic index confirmed that the fish fed on diets containing high levels of corn gluten meal and soybean meal evidenced a significant (P≤0.05) decrement of the HSI in relation to the utilization of glycogen, stored as an energy source.The results are in agreement with Lanari (2005) and Sampaio-Oliveira and Cyrino(2008).

Effects of the experimental diets on whole body protein concentration (Table 5) were very small with exception of fish diet containing FM, 25 and 50%PP which showed a significant difference (P≤0.05) compared to the other experimental diets (75 and 100%PP). Fish body fat content decreased with increasing level of PPs substitution. The low percentage of fat stored with diets containing high level of PPs is due to the limited ingestion of the feed or to probable use of the body fat as energy source and may be also related to the carbohydrate levels and type of the diets. These results are in agreement with Lanari (2005), Tibaldi

Table 6: Feed cost (l.E) for producing one Kg weight gain by sea bream (S. aurata) fingerlings fed on the experimental diets

Experimental diets

Cost(L.E)/kg

Relative fishmeal diets

Decrease in feed cost (%) FCR

Feed cost (L.E/Kg)

weight gain

Relative to fish meal diet

FM 6.56 100 0.00 1.64 10.76 100

PPs25 5.66 86.29 13.71 1.68 9.51 88.38

PPs50 4.77 72.71 27.29 1.89 9.02 83.83

PPs75 3.96 60.36 39.64 2.13 8.43 78.35

PPs100 3.12 47.56 52.44 2.31 7.21 67.01

The local market price were 8LE for fish meal, 2.50LE for gluten, 1.70LE for soybean meal, 1.00 LE for yellow corn, 9 LE for oil, 5 LE for Vit. & Min.


F: Process

meal in diet for turbot (Psetta maxima), Aquaculture 180: 99-117.

Robaina, L., Izquierdo, M.S., Moyamo, F.J., Socorro, J., Vergara, J.M., Montero, D. and Fernandez-Palacios, H.,(1995). Soybean and lupine seed meals as protein sources in diet for gilthead seabream (Sparus aurata), Nutritional and histological implication. Aquaculture, 130: 219-233.

Sampaio-Oliveira,A.M.B.M., and Cyrino,J.E.P.. (2008). Digestibilty of plant protein-based diets by largemouth bass Micropterus Salmoides, Aquaculture Nutrition , 14: 318-323.

Sitja-Bobadilla, A., Pena-Llopis, S., Gomez-Requeni, P., Medale, F., Kaushik, S., and Perez- Sanchez,J. (2005). Effect of fishmeal replacement by plant protein sources on non-specific difference mechanisms and oxidative stress in gilthead sea bream (Sparus aurata). Aquaculture, 249: 387-400.

Tibaldi, E., Hakim, Y., Uni, Z., Tulli, F., Francesco. D. M., Luzzana. U. and Harpaz. S., (2006). Effect of the partial substitution of dietary fishmeal by differently processed soybean meals on growth performance, nutrient digestibility and activity of intestinal brush border enzymes in the European sea bass ( Dicentrarchus labrax ). Aquaculture, 261. 182-193

Merinero, S., Martıńez-Llorens, S., Toma´ S, A. and Jover, M. (2005). Ana´ lisis econo´ mico de alternativas de produccio´ n de Dorada en jaulas marinas en el litoral Mediterrańeo espan˜ ol. Aquatic, 23: 1–19.

Morales, A.E., Cardenete, G., De La Higuera, M.,and Sanz, A. (1994). Effects of dietary protein source on growth, feed conversion and energy utilization in rainbow trout, Oncorhynchus mykiss. Aquaculture 124: 117–126.

Pereira, T.G. and Oliva-Teles, A., (2003). Evaluation of corn gluten meal as a protein source in diets for gilthead sea bream (Sparus avrata L.) juveniles. Aquaculture. Research, 34: 1111-1117.

Peres, H. and Oliva-Teles .A ., (2009). The optimum dietary essential amino acid profile for gilthead sea bream(Sparus aurata) juveniles. in press, Accepted Manuscript, Available on line 13 May 2009, Aquaculture.

Pongmaneerat, J., Watanabe, T., Takeuchi, T., and Satoh, S., (1993).Use of different protein Meals as partial or total substitution for fishmeal in carp diets. Bull. Jpn. Soc. Sci. Fish, 59: 1249- 1257.

Regost, C., Arzel,J., and Kaushik.S.J.(1999). Partial or total replacement of fishmeal by corn gluten

Hassanen, G.D.I. (1998). Lupin seed meal compared with soybean meal as partial substitutes for fishmeal in gilthead sea bream (Sparus aurata) diets. J. Agric. Sci. Mansoura Univ., 23(1) : 141-154.

Kaushik, S.J., Coves, D., Dutto, G. and Blanc, D.

(2004). Almost total replacement of fishmeal

by plant protein sources in the diet of a marine

teleost, the European seabass, Dicentrarchus

labrax. Aquaculture, 230: 391 – 404.

Lanari,D’.A., (2005). Alternative plant protein sources in sea bass diets, ITAL.J. ANIM. Sci. .4 : 365-374.

Lisac, D. and Muir, J. (2000). Comparative economics of offshore and on shore mariculture facilities. In: Mediterranean Offshore Mariculture. Options Me´diterraneénnes (Serie B: E´tudes et Recherches) (Muir, J. & Basurco, B. Eds), pp. 203–211. Publication Based on the Contents of the Advanced Course of the CIHEAM Network on Technology of Aquaculture in the Mediterranean (TECAM) Zaragoza, Spain, 1997.

Martınez-Llorens, S.,Vidal, A.T.; Garcia, I.J.; Torres, M.P. and Cerda, M.J. (2009) . Optimum dietary soybean meal level for maximizing growth and nutrient utilization of on growing gilthead sea bream (Sparus aurata), Aquaculture nutrition.15: 320- 328.


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